Pressure recovery device for an aircraft engine air intake

ABSTRACT

An aircraft includes a fuselage, an engine exhaust port extending through the fuselage, an air intake extending through the fuselage forward from, and adjacent to, the engine exhaust port, and an air cleaning assembly positioned over the air intake. The aircraft also includes a pressure recovery device including an outer wall positioned above the air cleaning assembly. A distance from a forward edge of the outer wall to the air cleaning assembly is greater than a distance from an aft edge of the outer wall to the air cleaning assembly. An inlet flow axis is defined normal to a cross-sectional flow area of the pressure recovery device at the forward edge, and is oriented upward at an acute angle relative to a longitudinal axis of the aircraft.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims priority to,U.S. application Ser. No. 15/949,815, filed Apr. 10, 2018, thedisclosure of which is incorporated by reference in its entirety.

FIELD

This disclosure relates to aircraft engine air intakes, and inparticular to intakes having filters, inertial particle separators orsimilar air permeable covers.

BACKGROUND

Some known air intakes for aircraft engines include an inlet thatgenerally conforms to a surface contour of the aircraft adjacent theintake. Such intakes may include a filter, air permeable cover orsimilar device that has an outer surface generally conformal to thelocal contour of the aircraft skin.

In some cases, a dynamic pressure of air flow into such an intake variessignificantly with the flight condition of the aircraft. For example,some rotary aircraft include an air intake that faces generally upward,such that the outer surface of the air permeable cover is generallyperpendicular to air flow at the intake while the aircraft is hovering,and generally parallel to airflow at the intake when the aircraft is inforward flight. As a result, the intake airflow in the forward flightcondition has a significantly lower dynamic pressure than in the hovercondition, which may result in comparatively reduced engine performance,or negatively affect performance, in forward flight. In at least somecases, it may be desirable to at least partially recover the dynamicpressure at the air intake in the forward flight condition. Moreover, anair intake that faces generally upward tends to expose the filter mediato ultraviolet radiation from the sun, or other environmental conditionswhich may accelerate the degradation of the filter media and necessitatemore frequent replacements of the filter assembly and/or filter media.Environmental conditions such as hail, driving rain, heavy snow or otherairborne debris can damage the filter assembly and or filter media.

This Background section is intended to introduce the reader to variousaspects of art that may be related to various aspects of the presentdisclosure, which are described and/or claimed below. This discussion isbelieved to be helpful in providing the reader with backgroundinformation to facilitate a better understanding of the various aspectsof the present disclosure. Accordingly, it should be understood thatthese statements are to be read in this light, and not as admissions ofprior art.

BRIEF DESCRIPTION

In one aspect, an aircraft is disclosed. The aircraft includes afuselage, an engine exhaust port extending through the fuselage, an airintake extending through the fuselage forward from, and adjacent to, theengine exhaust port, and an air cleaning assembly positioned over theair intake. The aircraft also includes a pressure recovery deviceincluding an outer wall positioned above the air cleaning assembly. Adistance from a forward edge of the outer wall to the air cleaningassembly is greater than a distance from an aft edge of the outer wallto the air cleaning assembly. An inlet flow axis is defined normal to across-sectional flow area of the pressure recovery device at the forwardedge, and is oriented upward at an acute angle relative to alongitudinal axis of the aircraft.

In another aspect, a method of shielding an air intake of an aircraftagainst engine exhaust gas recirculation is disclosed. The aircraftincludes a fuselage, an engine exhaust port extending through thefuselage, and an air intake extending through the fuselage forward from,and adjacent to, the engine exhaust port. The method includespositioning a pressure recovery device over the air intake. An aircleaning assembly is interposed between ambient air and the air intake,and a distance from a forward edge of an outer wall of the pressurerecovery device to the air cleaning assembly is greater than a distancefrom an aft edge of the outer wall to the air cleaning assembly. Themethod also includes orienting an inlet flow axis of the pressurerecovery device upward at an acute angle relative to a longitudinal axisof the aircraft. The inlet flow axis is defined normal to across-sectional flow area of the pressure recovery device at the forwardedge.

Various refinements exist of the features noted in relation to theabove-mentioned aspects. Further features may also be incorporated inthe above-mentioned aspects as well. These refinements and additionalfeatures may exist individually or in any combination. For instance,various features discussed below in relation to any of the illustratedembodiments may be incorporated into any of the above-described aspects,alone or in any combination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an aircraft of one embodiment.

FIG. 2 is a perspective view of an embodiment of an air cleaningassembly of an air intake assembly of the aircraft shown in FIG. 1.

FIG. 3 is an exploded perspective view of a pressure recovery deviceco-mounted with the air cleaning assembly shown in FIG. 2.

FIG. 4 is a perspective view of the pressure recovery device shown inFIG. 3 co-mounted with the air cleaning assembly shown in FIG. 3.

FIG. 5 is a front elevation view of the pressure recovery device shownin FIG. 3 co-mounted with the air cleaning assembly shown in FIG. 3.

FIG. 6 is a sectional view, taken along lines 6-6 shown in FIG. 5, of anembodiment of a forward edge of an outer wall of the pressure recoverydevice shown in FIG. 3.

FIG. 7 is a perspective view of an aircraft of another embodiment.

FIG. 8 is a perspective view of an embodiment of an air intake assemblyof the aircraft shown in FIG. 7.

FIG. 9 is a perspective view of another embodiment of the air intakeassembly of the aircraft shown in FIG. 7, in which an embodiment of apressure recovery device has a canted forward edge.

FIG. 10 is a perspective view of another embodiment of the air intakeassembly of the aircraft shown in FIG. 7, in which another embodiment ofthe pressure recovery device has a canted forward edge.

FIG. 11 is a perspective view of another embodiment of the air intakeassembly of the aircraft shown in FIG. 7, in which the pressure recoverydevice is oriented at an acute angle relative to a longitudinal axis ofthe aircraft.

FIG. 12 is a front elevation view of an embodiment of a cowlingincluding a plurality of air intake assemblies for use with an aircraft.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of an embodiment of an aircraft 100.Aircraft 100 is illustrated as a helicopter, and includes a generallyhorizontal primary rotor assembly 114 and a generally vertical tailrotor 110. Primary rotor assembly 114 includes a plurality of rotorblades 116. Alternatively, aircraft 100 may be, without limitation,another rotorcraft, a fixed wing airplane, a lighter than air vehicle,or combinations thereof. Aircraft 100 further includes a fuselage 104, acowling 106 mounted on the fuselage, and a cockpit 108. Propulsion poweris provided by a suitable engine (not shown) housed within the fuselage104 and/or cowling 106, such as a suitable turbine or piston internalcombustion engine. An air intake assembly 118 is positioned on thecowling 106 and is configured to channel air from outside the fuselage104 into an engine air intake 120 (shown in FIG. 2). Alternatively, theair intake assembly 118 may be positioned at any suitable location onthe fuselage 104. The aircraft 100 is associated with a direction offorward flight 111.

FIG. 2 is a perspective view of an embodiment of an air cleaningassembly 200 of the air intake assembly 118 of the aircraft 100. FIG. 3is an exploded perspective view of a pressure recovery device 300co-mounted with the air cleaning assembly 200. In the illustratedembodiment, the aircraft 100 is in a first condition (e.g., initiallymanufactured or delivered) without the pressure recovery device 300, andthe pressure recovery device 300 is retrofitted or co-mounted with theair cleaning assembly 200 in a retrofitting process. In alternativeembodiments, the aircraft 100 is initially manufactured with thepressure recovery device 300 co-mounted with the air cleaning assembly200.

The air cleaning assembly 200 includes a retention frame 210 mounted inthe cowling 106 and an air cleaning device 220 retained in the retentionframe. More specifically, the retention frame 210 interposes the aircleaning device 220 between the ambient air and the engine air intake,so that intake air is drawn through the air cleaning device 220 forremoval of particulates before flowing to the engine of the aircraft100.

The retention frame 210 includes a basket 212 sized to be received inthe engine air intake 120 in a clearance fit. The basket 212 defines aninterior cavity 218 sized to receive the air cleaning device 220. In theillustrated embodiment, the retention frame 210 also includes a screen222 that defines an exterior boundary of the interior cavity 218. Thescreen 222 defines a plurality of openings sized to inhibit debris andforeign objects in the environment surrounding the aircraft 100 fromreaching the air cleaning device 220 positioned beneath the screen.Moreover, the basket 212 and the screen 222 are configured to cooperateto securely retain the air cleaning device 220 in place within thebasket 212, yet allow for its easy replacement. In alternativeembodiments, the retention frame 210 is configured to retain the aircleaning device 220 in any suitable fashion that enables the aircleaning assembly 200 to function as described herein.

In the illustrated embodiment, the air cleaning device 220 is a filter221, formed from a pleated filter medium, and the basket 212 isconfigured to retain an upper contour 224 of the filter 221 against aninner surface of the screen 222. For example, the filter 221 is apleated sheet of porous material that has a particle removal efficiencyof at least about 96% of AC Coarse dust particles and at least about 95%of AC Fine dust particles from the intake air. As known in the art, ACCoarse (defined in Society of Automotive Engineers (SAE) J726 AirCleaner Test Code) dust has particle sizes ranging from 0 to 200 micronsand mean diameter of about 80 microns, and AC Fine dust has particlesizes ranging from 0 to 80 microns and mean diameter of about 8 microns.In alternative embodiments, the retention frame 210 is configured toretain any suitable device 220 for cleaning and/or conditioning theambient air channeled into the engine air intake 120, such as, but notlimited to, an inertial particle separator (e.g., vortex) air cleanerdevice (not shown).

The retention frame 210 also includes a lip 214 that extends around atleast a portion of the perimeter of the basket 212. For example, in theillustrated embodiment, the lip 214 extends around an entirety of theperimeter of the basket 212. The lip 214 is configured to extend over anouter skin 112 of the aircraft 100 surrounding the air intake assembly118 in face-to-face contact when the retention frame 210 is installed.

An exemplary material for the retention frame 210 is aluminum, althoughthe particular structure of the frame may vary by the type of aircraftand its specific design and configuration.

The retention frame 210 is substantially conformal, i.e., positionedalong or within, a moldline of the outer skin 112 of the aircraft 100.More specifically, the lip 214 is flush with the outer skin 112surrounding the air intake assembly 118 (e.g., the outer skin 112surrounding the air intake assembly 118 is recessed to accommodate athickness of the lip 214), slightly below flush, or slightly above flush(e.g., the outer skin 112 is not recessed). In addition, an exteriorsurface 230 of the air cleaning assembly 200 over the engine air intake120, defined by the screen 222 in the illustrated embodiment, iscontoured to conform to a contour of the outer skin 112 surrounding theair intake assembly 118. For example, in the illustrated embodiment, thecontour of the outer skin 112 surrounding the air intake assembly 118 isflat, and the exterior surface 230 is also flat. Alternatively, thecontour of the outer skin 112 surrounding the air intake assembly 118 iscurved, as shown in FIG. 8 for example, and the exterior surface 230 hasa curvature that matches the curved contour of the surrounding outerskin 112.

The pressure recovery device 300 includes an outer wall 310 that extendsover at least a portion of the basket 212 in a spaced-apartrelationship. More specifically, the outer wall 310 extends across theportion of the basket 212 between a pair of opposing side edges 316 thatare generally parallel to the direction of forward flight 111. The outerwall 310 also extends from a forward edge 320 to an aft edge 322.

The pressure recovery device 300 also includes a pair of side walls 312.Each side wall 312 is connected to a respective side edge 316 of theouter wall 310 and extends generally inward from the outer wall 310 toan inner edge 318 adjacent to the retention frame 210. The pressurerecovery device 300 further includes a pair of flanges 314 eachconnected to the inner edge 318 of a respective side wall 312. Morespecifically, the flanges 314 are configured to extend over the lip 214of the retention frame 210 in face-to-face contact when the pressurerecovery device 300 is installed, such that the flange, the lip, and theouter skin underneath the lip are substantially parallel, and the sidewalls 312 are configured to space the outer wall 310 apart from thebasket 212. A plurality of openings 332 is defined in the flanges 314,and each opening 332 is configured to align with a respective opening132 defined in the outer skin 112 and a respective opening 232 definedin the lip 214 of the retention frame 210.

In some embodiments, the pressure recovery device 300 is formedrelatively simply and inexpensively by stamping and folding a singlepiece of sheet metal to form outer wall 310, side walls 312, and flanges314. In alternative embodiments, the pressure recovery device 300 isformed in any suitable fashion, from any suitable materials and anysuitable number of individual components.

In the illustrated embodiment, for the aircraft 100 as initiallydelivered, that is, before the pressure recovery device 300 isinstalled, the retention frame 210 is secured to the cowling 106 by aplurality of initial fasteners 202 (shown in FIG. 2). In alternativeembodiments, the retention frame 210 is secured to the cowling 106 inany suitable fashion that enables the retention frame 210 to function asdescribed herein. In the illustrated embodiment, each initial fastener202 is sized to extend through a respective opening 232 in the lip 214of the frame 210, and into an aligned respective opening 132 in theouter skin 112. For example, the initial fasteners 202 are metal boltsor screws having a length selected to fit the aligned openings 232 and132. Alternatively, the initial fasteners 202 are any suitable fastenersthat enable the retention frame 210 to function as described herein. Theinitial fasteners 202 have a rated strength selected to secure, with theappropriate safety factors, the air cleaning assembly 200 to theaircraft 100.

In the illustrated embodiment, to install the pressure recovery device300 in a retrofit process, the initial fasteners 202 are removed fromthe corresponding pairs of aligned openings 132 and 232 definedrespectively in the outer skin 112 and the lip 214. The pressurerecovery device 300 is positioned over the air cleaning assembly 200such that the openings 332 in the flanges 314 register with the alignedopenings 132 and 232. A plurality of replacement fasteners 302 (shown inFIG. 3) is then installed into each aligned trio of openings 332, 232,and 132. The replacement fasteners 302 have certain size parameters(e.g., diameter, thread configuration) substantially identical to theinitial fasteners 202, in order to be received in and cooperate with theopening 232 in the lip 214 of the air cleaning assembly 200 and theopening 132 in the outer skin 112. However, in some embodiments, thereplacement fasteners 302 have a greater length than the initialfasteners 202 to accommodate a thickness of the flange 314. Additionallyor alternatively, in certain embodiments, the replacement fasteners 302have a greater rated strength than the initial fasteners 202 to ensurethat the pressure recovery device 300, which during operation ofaircraft 100 typically encounters higher dynamic forces than the aircleaning assembly 200 by itself prior to the retrofit, is suitablysecured to the aircraft 100. In alternative embodiments, the initialfasteners 202 have sufficient length and/or strength to be re-used inthe retrofit process. In other alternative embodiments, the aircraft 100is initially manufactured or delivered with the pressure recovery device300, and the initial fasteners 202 are accordingly sized at the time ofmanufacture.

FIG. 4 is a perspective view of the pressure recovery device 300co-mounted with the air cleaning assembly 200 to form the air intakeassembly 118. FIG. 5 is a front elevation view, i.e., with the forwardflight direction 111 pointing normal to and out of the page, of the aircleaning assembly 200 and the co-mounted pressure recovery device 300.As can be seen, the outer wall 310 generally slopes downward andafterward relative to the exterior surface 230 of the air cleaningassembly 200. More specifically, a distance 340 from the forward edge320 of the outer wall 310 to the air cleaning assembly 200 is greaterthan a distance 342 from the aft edge 322 of the outer wall 310 to theair cleaning assembly 200. As can be seen in FIG. 5, the distance fromthe outer wall 310 to the air cleaning assembly 200 is measured normalto the exterior surface 230 of the air cleaning assembly 200. Moreover,the distance from the outer wall 310 to the air cleaning assembly 200generally tapers between the forward edge 320 and the aft edge 322, suchthat a cross-sectional flow area of the pressure recovery device 300likewise tapers between the forward edge 320 to the aft edge 322. Thecross-sectional flow area is defined normal to the forward flightdirection 111 of the aircraft 100. In the illustrated embodiment, theouter wall 310 slopes linearly from the forward edge 320 down towardsthe aft edge 322. In alternative embodiments, the distance between theouter wall 310 and the exterior surface 230 is tapered in any suitablefashion that enables the pressure recovery device 300 to function asdescribed herein.

The afterward tapering of the cross-sectional flow area of the pressurerecovery device 300, as described above, facilitates a more levelpressure recovery versus velocity curve for the air intake assembly 118as the aircraft 100 transitions from hovering into forward flight. Morespecifically, when the aircraft 100 is taking off vertically orhovering, a dynamic pressure of ambient air entering the air cleaningassembly 200 is primarily driven by downwash from the rotor assembly114. Exterior surface 230 of the air cleaning assembly 200 is shieldedby outer wall 310 from direct impingement, but the relatively uniformvertical speed of the ambient air on all sides of the pressure recoverydevice 300 provides ram air pressure to the intake air resulting in arelatively high pressure recovery across the air cleaning assembly 200.When the aircraft 100 transitions into forward motion, the forwardvelocity of the ambient air becomes greater than the downwash velocity,so that exterior surface 230 is now oriented parallel to the primarydirection of flow. In the absence of the pressure recovery device 300,the pressure recovery at the engine from parallel flow over the surface230 of the air cleaning assembly 200 would be greatly reduced. However,the tapering cross-sectional flow area defined by the pressure recoverydevice 300 over the exterior surface 230 tends to increase the ram airpressure into the air cleaning assembly 200 in concert with increasingair speed in the direction of forward flight 111. Thus, in either hoveror forward flight, the engine air intake 120 receives air with goodpressure recovery through the air cleaning assembly 200 so that pressuredrop across the air intake assembly 118 is somewhat constant withairspeed. The pressure of intake air provided to the engine is thusstabilized during transitional flight, and enhances engine performanceduring forward flight. It should also be noted that, in someembodiments, the outer wall 310 extending over at least a portion of thebasket 212 in a spaced-apart relationship facilitates shielding thefilter 221 from ultraviolet radiation from the sun, thus slowing thedegradation of the filter media and resulting in less frequentreplacements of the filter 221.

In the illustrated embodiment, the distance 342 from the aft edge 322 ofthe outer wall 310 to the air cleaning assembly 200 is non-zero, suchthat a gap 350 is defined between the aft edge 322 of the outer wall andthe air cleaning assembly 200. More specifically, the gap 350 is sizedto enable snow, ice, or other airborne particulates captured at theforward edge 320 to pass through the pressure recovery device 300 andexit the aft edge 322, thereby limiting obstruction to the air flow intothe air cleaning assembly 200.

In some embodiments, a size of the pressure recovery device 300 isselected to tailor a pressure recovery profile. For example, in theillustrated embodiment, the forward edge 320 of the outer wall 310extends forward of a forward edge of the filter 221, which increases theram air pressure into the air cleaning assembly 200 relative to a moreaft positioning of the forward edge 320 of the outer wall. Additionallyor alternatively, the aft edge 322 of the outer wall 310 extends aft ofan aft edge of the filter 221.

FIG. 6 is a sectional view, taken along lines 6-6 shown in FIG. 5, of anembodiment of the forward edge 320 of outer wall 310 of the pressurerecovery device 300. In the illustrated embodiment, forward edge 320defines an airfoil shape. In some embodiments, the airfoil shape offorward edge 320 reduces drag of an airflow over pressure recoverydevice 300 during forward flight of aircraft 100. In alternativeembodiments, forward edge 320 of outer wall 310 defines any suitableshape that enables pressure recovery device 300 to function as describedherein.

FIG. 7 is a perspective view of another embodiment of the aircraft 100.The illustrated aircraft 100 is similar to the aircraft of FIG. 1, butincludes the air intake assembly 118 positioned on another cowling 106at a different location on the fuselage 104, just forward of an engineexhaust port 122 with respect to a longitudinal axis 107 of the aircraft100 that extends from a nose to a tail of the aircraft 100.Alternatively, the air intake assembly 118 may be positioned at anysuitable location on the fuselage 104.

FIG. 8 is a perspective view of an embodiment of the air intake assembly118 of the aircraft 100 shown in FIG. 7. The air intake assembly 118 issimilar to the air intake assembly shown in FIG. 3, except for thefollowing differences. The contour of the outer skin 112 surrounding theair intake assembly 118 is curved, and the exterior surface 230 of theair cleaning assembly 200 has a curvature that matches the curvedcontour of the surrounding outer skin 112. The outer wall 310 of thepressure recovery device 300 is likewise curved to follow the contour ofthe exterior surface 230 as the outer wall slopes downward andafterward, again defining the tapered cross-sectional flow area andproviding the pressure recovery benefits discussed above. In theillustrated embodiment, the flanges 314 of the pressure recovery device300 are also contoured to fit flush against the lip 214 (shown in FIG.3) of the air cleaning assembly 200. In some embodiments, in addition tothe other benefits described above, the pressure recovery device 300extending over at least a portion of the exterior surface 230 alsofacilitates protecting the air intake 120 against exhaust gasrecirculation from the exhaust port 122 in close proximity. In effect,the pressure recovery device 300 acts as a shield against the hotexhaust gas from the port 122, inhibiting the entry of hot exhaust gasinto the intake 120. Moreover, the pressure recovery device 300 may beadded to existing air cleaning assemblies 200 in a retrofit process asdescribed above, advantageously improving a performance envelope ofexisting aircraft in a relatively fast and inexpensive fashion.

As shown in FIG. 8, the cross-sectional flow area of the pressurerecovery device 300 at the forward edge 320 of the outer wall 310 isoriented generally normal to the longitudinal axis 107 of the aircraft100. In other words, the opposing side walls 312 are oriented generallyparallel to the longitudinal axis 107 and the forward flight direction111. An advantage of the illustrated orientation of the pressurerecovery device 300 is that the resulting dynamic pressure recovery forthe engine air intake 120 is substantially increased when the aircrafttravels in the forward flight direction 111.

FIGS. 9-11 are perspective views of additional embodiments of the airintake assembly 118 of the aircraft 100 shown in FIG. 7. In each of theembodiments of FIGS. 9-11, an inlet flow axis 326 of the pressurerecovery device 300 is oriented upward at an acute angle 330 relative tothe longitudinal axis 107 of the aircraft 100. The acute angle 330 ofthe inlet flow axis 326 provides certain advantages in enabling dynamicpressure recovery while inhibiting re-ingestion of exhaust gases fromthe exhaust port 122, as will be described below. The inlet flow axis326 is defined normal to a cross-sectional flow area of the pressurerecovery device 300 at the forward edge 320, and the acute angle 330 maybe achieved in several different ways.

For example, the air intake assembly 118 illustrated in FIG. 9 issimilar to the air intake assembly shown in FIG. 8, except as describedbelow. First, the flanges 314 of the pressure recovery device 300 arerotated 90 degrees relative to the orientation in FIG. 8, such that theopposing side walls 312 are aligned generally vertically. As a result,one of the side walls 312, rather than the gap at the aft edge 322 as inFIG. 8, faces the exhaust port 122. In some embodiments, the side wall312 facing the exhaust port 122 tends to block a direct flow path ofexhaust gas from the exhaust port 122 to re-ingestion through the aircleaning assembly 200 into the engine air intake 120.

Second, in the embodiment of FIG. 9, the forward edge 320 of the outerwall 310 is canted relative to the flanges 314. As a result, the inletflow axis 326 is oriented partially forward at the acute angle 330 tothe longitudinal axis 107 of the aircraft 100. In other words, thecross-sectional flow area at the forward edge 320 faces at leastpartially towards the forward flight direction 111. The canted forwardedge 320 thus enables the pressure recovery device 300 to providesignificant dynamic pressure recovery for the engine air intake 120 whenthe aircraft 100 travels in the forward flight direction 111. Forembodiments in which the aircraft 100 is a helicopter, a furtheradvantage of the acute angle 330 is that when the helicopter is in asubstantially hovering condition, the pressure recovery device 300captures downwash from the rotor assembly 114 (as shown in FIG. 7),which tends to dissipate and/or dilute exhaust gas from exhaust port 122that otherwise would be susceptible to re-ingestion through the aircleaning assembly 200 into the engine air intake 120.

In the embodiment illustrated in FIG. 9, the side wall 312 that facesthe exhaust port 122 is substantially co-extensive with the adjacentflange 314. The forward edge 320 of the outer wall 310 extends forwardfrom the co-extensive side wall 312 and is canted downward towards theopposing side wall 312, such that a portion 215 of the air cleaningassembly 200 is not covered by the outer wall 310. However, an advantageof the embodiment of FIG. 9 is that the flanges 314 may be securedthrough the lip 214 (shown in FIG. 3) of the air cleaning assembly 200,such as in a retrofit process, in the same manner as described abovewith respect to FIGS. 3-5.

For another example, the air intake assembly 118 illustrated in FIG. 10is similar to the air intake assembly shown in FIG. 9, except that theside wall 312 that faces in the forward flight direction 111 issubstantially co-extensive with the adjacent flange 314. The forwardedge 320 of the outer wall 310 extends afterward from the co-extensiveside wall 312 and is canted upward towards the opposing side wall 312,such that a portion 315 of the aft flange 314 extends for a significantdistance beyond the lip 214 (shown in FIG. 3) through which the flange314 is secured. As a result, the inlet flow axis 326 is again orientedpartially forward at the acute angle 330 to the longitudinal axis 107 ofthe aircraft 100. In some embodiments, the flanges 314 are again securedthrough the lip 214 (shown in FIG. 3) of the air cleaning assembly 200in the same manner as described above with respect to FIGS. 3-5. Foradditional stability, the extended portion 315 of the aft flange 314 maybe further secured directly to the cowling 106, for example using anadhesive, a welded joint, or an auxiliary fastener. An advantage of theembodiment of FIG. 10 is that the outer wall 310 covers substantially anentirety of the air cleaning assembly 200.

In the embodiments illustrated in FIGS. 9 and 10, the aft edge 322 isnot canted, and is oriented generally perpendicular to the flanges 314.In alternative embodiments, the aft edge 322 is oriented in any suitablefashion that enables the pressure recovery device 300 to function asdescribed herein.

For another example, the air intake assembly 118 illustrated in FIG. 11is similar to the air intake assembly shown in FIG. 8, except that theflanges 314 of the pressure recovery device 300 are not mounted to thelip 214 (shown in FIG. 3) of the air cleaning assembly 200. Instead, thepressure recovery device 300 is mounted to the cowling 106 separatelyfrom the mounting means used for the air cleaning assembly 200. Forexample, the pressure recovery device 300 is mounted directly to thefuselage by welding the flanges 314 to the cowling 106 or insertingauxiliary fasteners through the flanges 314 into the cowling 106. Thebody of the pressure recovery device 300 is oriented such that the inletflow axis 326, defined normal to the cross-sectional flow area of thepressure recovery device 300 at the forward edge 320 of the outer wall310 as discussed above, is again oriented at the acute angle 330 to thelongitudinal axis 107 of the aircraft 100. However, in this embodimentthe acute angle 330 is achieved without any need to cant the forwardedge 320 relative to the flanges 314. Instead, the flanges 314 also areoriented substantially at the acute angle 330 relative to thelongitudinal axis 107.

In the embodiment illustrated in FIG. 11, similar to the embodimentsillustrated in FIGS. 9 and 10, one of the side walls 312 faces theexhaust port 122 and tends to block a direct flow path of exhaust gasfrom the exhaust port 122 to re-ingestion through the air cleaningassembly 200 into the engine air intake 120. Also similarly, forembodiments in which the aircraft 100 is a helicopter, the acute angle330 enables the pressure recovery device 300 to capture downwash fromthe rotor assembly 114 (shown in FIG. 7) when the helicopter is in asubstantially hovering condition, which tends to dissipate and/or diluteexhaust gas from exhaust port 122 that otherwise would be susceptible tore-ingestion through the air cleaning assembly 200 into the engine airintake 120.

In some embodiments, the advantages of dynamic pressure recovery andinhibition of exhaust gas re-ingestion, as discussed above with respectto FIGS. 9 through 11, are obtained for the acute angle 330 in a rangefrom about 20 degrees to about 80 degrees. In certain embodiments, theacute angle 330 being about 45 degrees provides significant exhaust gasdissipation/dilution while the aircraft 100 is in hover, while stillproviding significant dynamic pressure recovery for the engine airintake 120 when the aircraft 100 travels in the forward flight direction111.

FIG. 12 is a front elevation view, i.e., with the forward flightdirection 111 pointing normal to and out of the page, of anotherembodiment of the cowling 106 including a plurality of air intakeassemblies 118. In the illustrated embodiment, the outer skin 112 of thecowling 106 defines a generally cylindrical shape having a longitudinalaxis substantially parallel to the forward flight direction 111 of theaircraft 100, and the air intake assemblies 118 are arranged about acircumference of the outer skin 112. More specifically, in theillustrated embodiment, three air intake assemblies 118 are spacedevenly around the circumference of the cylinder defined by the outerskin 112. The air cleaning assembly 200 of each of the plurality of airintake assemblies 118 is configured to channel air from outside thecowling 106 into a common engine air intake 120 central to the cylinder.In alternative embodiments, the outer skin 112 of the cowling 106defines any suitable shape, and the cowling includes any suitable numberof air intake assemblies 118 arranged in any suitable fashion about theouter skin, that enables air intake assemblies 118 to function asdescribed herein.

Each of the air intake assemblies 118 includes elements substantiallyidentical to those described above with respect to FIGS. 2-5, except asotherwise noted below. For example, each of the air cleaning assemblies200 includes the lip 214 (shown in FIG. 3) secured to the cowling 106,and the exterior surface 230 contoured to conform to the contour of theouter skin 112 surrounding the air intake assembly 118, as describedabove. Specifically, in the illustrated embodiment, the exterior surface230 is again contoured to conform to the cylindrical shape defined bythe outer skin 112 surrounding the respective air intake assembly 118.For example, the air cleaning device 220 is again the filter 221 (shownin FIG. 3) formed from a pleated filter medium, and the basket 212 hasan arcuate shape concentric with the screen 222 and configured to retainthe pleated folder medium having the upper contour 224 (shown in FIG. 3)in a corresponding arcuate configuration against the inner surface ofthe screen that defines the exterior surface 230. Likewise, a sectionalshape of the outer wall 310, in each plane normal to the forward flightdirection 111, is arcuate and concentric with the contour of theexterior surface 230. In alternative embodiments, the basket 212 has anysuitable shape that enables the exterior surface 230 of the air cleaningassembly 200 to conform to the contour of the outer skin 112, and theouter wall 310 has any correspondingly suitable sectional shape in theplane normal to the forward flight direction 111.

Further in the illustrated embodiment, each of the pressure recoverydevices 300 includes the flange 314 secured to the lip of acorresponding one of the air cleaning assemblies 200, and the outer wall310 spaced from the exterior surface 230 of the corresponding one of theair cleaning assemblies and defining a tapered cross-sectional flow areaas described above.

Although the air intake assembly 118 has been illustrated as mounted inthe outer skin 112 having a substantially flat local contour (FIGS.2-5), a simply curved local contour (FIGS. 7-11), and a generallycylindrical local contour (FIG. 12), it should be understood thatembodiments of the air intake assembly 118 described herein are not solimited. Rather, the air intake assembly 118 is adaptable to anysuitable local contour of the outer skin 112 of the aircraft 100. Theinclusion of the pressure recovery device 300 facilitates stabilizingthe pressure of intake air delivered to the engine during transitionalflight and enhancing engine performance during forward flight, asdescribed above. In some embodiments, the pressure recovery device 300extending over at least a portion of the basket 212 also facilitatesshielding the filter 221 from ultraviolet radiation from the sun.Moreover, the pressure recovery device 300 may be added to existing aircleaning assemblies 200 in a retrofit process as described above,advantageously improving a performance envelope of existing aircraft ina relatively fast and inexpensive fashion.

When introducing elements of the present invention or the embodiment(s)thereof, the articles “a”, “an”, “the” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising”,“including” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

As various changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. An aircraft comprising: a fuselage; an engineexhaust port extending through the fuselage; an air intake extendingthrough the fuselage forward from, and adjacent to, the engine exhaustport; an air cleaning assembly positioned over the air intake; and apressure recovery device including an outer wall positioned above theair cleaning assembly, wherein: a distance from a forward edge of theouter wall to the air cleaning assembly is greater than a distance froman aft edge of the outer wall to the air cleaning assembly; and an inletflow axis is defined normal to a cross-sectional flow area of thepressure recovery device at the forward edge, and is oriented upward atan acute angle relative to a longitudinal axis of the aircraft.
 2. Theaircraft of claim 1, wherein the air cleaning assembly further includesa lip secured to an outer skin of the fuselage, and the pressurerecovery device further includes opposing flanges mounted to the lip. 3.The aircraft of claim 2, wherein the forward edge of the outer wall ofthe pressure recovery device is canted relative to the flanges.
 4. Theaircraft of claim 1, wherein a gap is defined between the aft edge ofthe outer wall and the air cleaning assembly, the gap sized to enablepassage of particulates through the pressure recovery device.
 5. Theaircraft of claim 1, wherein the pressure recovery device furtherincludes opposing flanges, and wherein the flanges are orientedsubstantially at the acute angle relative to the longitudinal axis ofthe aircraft.
 6. The aircraft of claim 1, wherein the pressure recoverydevice further includes opposing flanges, and wherein the flanges aremounted to the fuselage separately from the air cleaning assembly. 7.The aircraft of claim 1, wherein the cross-sectional flow area of thepressure recovery device generally tapers between the forward edge ofthe outer wall and the aft edge of the outer wall.
 8. The aircraft ofclaim 1, wherein the forward edge of the outer wall defines an airfoilshape.
 9. The aircraft of claim 1, wherein the air cleaning assemblyfurther includes a filter interposed between ambient air and the airintake.
 10. The aircraft of claim 1, wherein the air cleaning assemblyfurther includes: a basket sized to be received in the air intake in aclearance fit, wherein the basket defines an interior cavity sized toreceive a filter; and a lip extending around at least a portion of aperimeter of the basket.
 11. The aircraft of claim 10, wherein the aircleaning assembly further includes a screen configured to cooperate withthe basket to securely retain the filter in place within the basket, andwherein the screen defines an exterior surface of the air cleaningassembly.
 12. The aircraft of claim 10, wherein the filter is formedfrom a pleated filter medium.
 13. The aircraft of claim 12, wherein thepleated filter medium has a particle removal efficiency of at leastabout 96% of AC Coarse dust particles and at least about 95% of AC Finedust particles.
 14. The aircraft of claim 10, wherein the lip of the aircleaning assembly is substantially flush with an outer skin of thefuselage.
 15. A method of shielding an air intake of an aircraft againstengine exhaust gas recirculation, wherein the aircraft includes afuselage, an engine exhaust port extending through the fuselage, and anair intake extending through the fuselage forward from, and adjacent to,the engine exhaust port, the method comprising: positioning a pressurerecovery device over the air intake, wherein: an air cleaning assemblyis interposed between ambient air and the air intake, and a distancefrom a forward edge of an outer wall of the pressure recovery device tothe air cleaning assembly is greater than a distance from an aft edge ofthe outer wall to the air cleaning assembly; and orienting an inlet flowaxis of the pressure recovery device upward at an acute angle relativeto a longitudinal axis of the aircraft, wherein the inlet flow axis isdefined normal to a cross-sectional flow area of the pressure recoverydevice at the forward edge.
 16. The method of claim 15, wherein the aircleaning assembly further includes a lip secured to an outer skin of thefuselage, the method further comprising mounting opposing flanges of thepressure recovery device to the lip.
 17. The method of claim 16, whereinthe forward edge of the outer wall of the pressure recovery device iscanted relative to the flanges, causing the inlet flow axis to beoriented at the acute angle when the flanges are mounted to the lip. 18.The method of claim 15, wherein the pressure recovery device furtherincludes opposing flanges, and wherein orienting the inlet flow axisupward at the acute angle comprises orienting the flanges substantiallyat the acute angle relative to the longitudinal axis of the aircraft.19. The method of claim 15, wherein the pressure recovery device furtherincludes opposing flanges, the method further comprising mounting theflanges to the fuselage separately from the air cleaning assembly. 20.The method of claim 15, further comprising: removing each of a pluralityof initial fasteners from a corresponding pair of aligned openingsdefined respectively in a lip of the air cleaning assembly and an outerskin of the fuselage, wherein positioning the pressure recovery devicefurther comprises registering each of a plurality of openings defined ina flange of the pressure recovery device with one of the pairs ofaligned openings to form a corresponding aligned trio of openings; andinstalling a respective replacement fastener into each aligned trio ofopenings.